fluid vs liquefied petroleum gas

fluid

noun
  • A liquid (as opposed to a solid or gas). 

  • Any substance which can flow with relative ease, tends to assume the shape of its container, and obeys Bernoulli's principle; a liquid, gas or plasma. 

  • Intravenous fluids. 

adj
  • In a state of flux; subject to change. 

  • Of or relating to fluid. 

  • Moving smoothly, or giving the impression of a liquid in motion. 

  • Convertible into cash. 

  • Genderfluid. 

liquefied petroleum gas

noun
  • A mixture of propane and butane with traces of some other gases, which is kept in a liquid state at high pressure in metal bottles, and used as a source of gas for cooking, heating and as a fuel in internal combustion engines in vehicles. 

How often have the words fluid and liquefied petroleum gas occurred in a corpus of books? (source: Google Ngram Viewer )